Ethylenedinitrilotetraacetic acid is a well-known and widely used chelating agent. It does not appear that there have been compounds available which result from the substitution of a functional group capable of reacting with a biological macromolecule for one or more of the hydrogen atoms of the ethylene group of ethylenedinitrilotetraacetic acid. Compounds having such substituents would vary in chelating activity of the molecule and would open the way to ethylenedinitrilotetraacetic acid-metal chelates having varied chemical and physical properties and extending utility.
U.S. Pat. No. 3,665,192 describes a method for studying the behavior of biological macromolecules by attaching a radioactive label to the macromolecule and then observing the extent of perturbation of the angular correlation of the radiation emitted by the radioactive label. The method is sophisticated but it opens the way to more definitive study of the structures of biological macromolecules.
In order to make efficient use of this technique, it is necessary to have available radioactive labels which will attach and adhere to the macromolecules to be studied. An effective label would be a radioactive metal ion bound by a powerful chelating agent which in addition to its metal sequestering groups contains an active functional group which can bond the metal chelate to a biological macromolecule. Such effective labels are produced pursuant to this invention by (1) producing N,N'-diacetyl 1-phenylethylenediamine and (2) introducing a functional group into its benzene ring, for example by subjecting it to nitration, nitration and reduction, sulfonation or acylation, (3) hydrolyzing the reaction products and (4) reacting each hydrolysis product with Bromoacetic acid. In this manner ethylene dinitrilotetraacetic acids of the formula ##SPC1##
In which X is a functional group, are produced. Groups such as NO.sub.2, NH.sub.2, SO.sub.3 H, ##STR1## OH, COOH provide the desired functionality.